Traditionally, litter boxes for cats have included a shallow box-shaped device, open at the top, which contains cat litter. A cat steps into the box and deposits waste material into the litter. These open cat litter boxes have several disadvantages. The open nature of these boxes does very little to contain or control the unpleasant odors from the animal waste material. Consequently, such boxes are typically placed at a remote location in the residence. Also, this type of cat box requires periodic efforts by the cat owner to remove the animal waste material, replace the litter on occasion, and on a less frequent basis, wash the cat litter box. In addition, due to the tendency of cats to dig, kick, and otherwise distribute the litter within the cat box, it is common for a fair amount of litter or waste to be kicked out of the shallow cat box. Depending on the habits of the individual cat, the cat sometimes "misses the litter box" and deposits the waste on the side of the device because the low sides of the device do not prevent this behavior. Further, a significant amount of litter is tracked out of the cat box on the bottom of the cat's paws. All of this results in an undesirable collection of cat litter on the ground surrounding the cat box. Some of these problems have been addressed by cat litter boxes which include higher side walls and a top and have openings at one or either end to allow the cat to enter and exit the box. Some of these boxes contain deodorizing materials in the box to help to mask the unpleasant odors from the animal waste material. These boxes address some of the problems discussed above while failing to address others. In addition, recent developments in litter technology have provided "clumpable" litter which creates a clump of litter around liquid waste material, making it easier to scoop out this material.
More of the problems have been addressed in a manual cat litter device disclosed in U.S. Pat. No. 4,120,264. This device includes a manually rotating drum resting on a support base having rollers thereon. The drum is partially enclosed on either end with an opening found in each end. A first opening allows the cat to enter and exit the drum to deposit waste material in the cat litter contained therein. A second opening on the opposite end of the drum places a waste storage bag in communication with the interior of the drum. A complex arrangement of screens are mounted within the drum to communicate with the second opening. When the cat owner desires to remove the waste material from the drum, he can rotate the drum manually relative to the support base through a single, full rotation so that the litter passes through the screens and the animal waste material is "filtered-out" and directed toward the second opening where it is expelled from the drum into the waste storage bag. While providing some improvements, this approach has several disadvantages. First of all, the device is manual, requiring operator actuation which may result in the device going through long periods without an operational cycle. Second, even in the waste storage bag, the waste material is not closed off from the surrounding environment so that unpleasant odors can still pass from the waste storage bag through the drum to the surrounding environment. Third, no measures have been taken to prevent undesired tracking of the litter out of the drum by the cat. Fourth, because of the two openings on opposite sides of the drum, both sides of the device must be accessible. The front must be accessible for the cat to enter and exit the drum and the back must be accessible for the owner to change waste storage bags.
A motorized cat litter device is disclosed in U.S. Pat. No. 4,846,104. This device includes a motor-driven rotating drum which appears to be axially mounted to a support base which includes a waste storage area for receiving the waste discharged from the rotating drum. The rotating drum includes an inner compartment defined therein and a screen associated therewith. A single opening is provided in the outer circumference of the rotating drum to allow for ingress and egress of the animal as well as expulsion of the waste material from the drum. The drum is rotated through a full rotation so that the clean litter passes through the screen while the waste material is filtered-out by the screen and directed out of the single opening into the waste storage area in the support base. This device solves some of the problems described above while neglecting to address others. One significant disadvantage of the approach is that the clean litter is dumped a significant distance from the inner compartment to the bottom portion of the drum as shown in FIG. 5D of U.S. Pat. No. 4,846,104. This action together with the fact that the litter is forced to pass through the screen a second time causes the cat litter to be broken into smaller bits and creates a significant cloud of dust on each cycle. Portions of these dust clouds exit the rotating drum and fall out as dust on the ground in the vicinity of the cat litter device. Also, the device apparently must be accessible on opposite sides for use and for cleaning, which is inconvenient and limits the locations for convenient placement of the device in the residence. In addition, there are sanitation concerns arising from the use of the waste outlet as the animal entrance/exit.
It is against this background and the desire to solve the problems of the prior art that the present invention has been developed.